The time to fill a pool of water, b is 2 hours, so b is the water injection pipe.

B and c are 15 hours, so c is a drain pipe.

C and d are 6 hours, so d is the water injection pipe.

D and e are 3 hours, so e is a drain.

E and a are 10 hour, so a is the water injection pipe.

work efficiency

B is 2 hours, and C is 15 hours.

1/2-1/c =1151/c =13/30 c It takes 30/ 13 hours to drain.

Maximum water injection rate

C and d are six hours.

1/d-13/30 =1/61/d =18/30 days. Water injection takes 30/ 18 hours.

In the same way; In a similar way

D and e are 3 hours, 1/E=8/30 E, and drainage takes 30/8 hours.

E and a are 10 hour 1/A= 1 1/30.

therefore

The maximum water injection speed of d D water injection is 30/ 18 hours.

E, which has the highest drainage efficiency, needs 30/8 hours for drainage.